Chemistry 1st Semester Interim Review

Use the information and models to answer the following question. Models help scientists visualize concepts. Five models are shown. Which of the following models would represent the MOST reactive nonmetals?

• Models 1 and 3

• Models 4 and 5

• Model 1, 2, and 3

• Models 1, 3, and 4

Answer explanation

Models 1 and 3 likely represent the most reactive nonmetals, as they correspond to elements like fluorine and chlorine, which are known for their high reactivity. Other models may depict less reactive nonmetals. (Group 7 is very reactive. It wants 1 more electron to have a full octet.)

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

What is the ion configuration of the chlorine ion, Cl⁻?

• 1s²2s²2p⁶3s²3p³

• 1s²2s²2p⁶3s²3p⁴

• 1s²2s²2p⁶3s²3p⁵

• 1s²2s²2p⁶3s²3p⁶

Answer explanation

The chlorine ion, Cl⁻, has gained one electron, resulting in a total of 18 electrons. Its electron configuration is 1s²2s²2p⁶3s²3p⁶, which matches the configuration of argon, indicating a stable octet.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

Use the model to answer the following question. Which of the following explanations are TRUE regarding the mass number and identity of Element C?

• Element C has only a different identity than elements A and B

• Element C has only a different mass number than elements A and B

• Element C has the same mass number and identity as elements A and B

• Element C has both a different mass number and identity than elements A and B

Answer explanation

Element C has a different mass number and identity than elements A and B, indicating it is a distinct element. (It has a different number of protons which determines the identity and a different number of protons + neutrons which determines the mass number)

Tags

NGSS.HS-PS1-8

Which of the following statements must be TRUE regarding nuclear fusion?

• The mass of the produced atom is less than the mass of the original nuclei and the identity is the same.

• The mass of the produced atom is less than the mass of the original nuclei and the identity is different.

• The mass of the produced atom is greater than the mass of the original nuclei and the identity is different.

• The mass of the produced atom is greater than the mass of the original nuclei and the identity is the same.

Answer explanation

Nuclear fusion is the process by which two light atomic nuclei combine to form a single heavier one while releasing massive amounts of energy.

Tags

NGSS.HS-PS1-8

Use the information to answer the following question. What is the identity of the unknown element and why is the color emitted?

• Strontium, because electrons move from ground state to excited state to emit light

• Strontium, because as electrons fall back from an excited state to ground state they emit light

• Potassium, because electrons move from a ground state to an excited state to emit light

• Potassium, because as electrons fall back from an excited state to ground state they emit light

Answer explanation

The correct choice is Strontium, as the unknown emits a red color and Strontium also emits a red color. Light is emitted when electrons fall back from an excited state to the ground state.

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

NGSS.HS-PS4-3

Use the information and table to answer the following question. A sample of phosphorus was isolated and analyzed to determine the percent abundance of each isotope. The results are recorded in the table.

• When the masses of 29, 31, and 32 are added and divided by 3 the average is closest to 31.

• Phosphorus-31 has the greatest percent abundance so the average atomic mass should be 31.

• The mass of phosphorus-31 is between phosphorus-29 and phosphorus-32. The average atomic mass is in the middle of the isotope’s masses.

• All isotopes of phosphorus have 15 protons and 16 neutrons. When protons and neutrons are added together, the average mass would be 31.

Answer explanation

Phosphorus-31 is the most abundant isotope, which means it significantly influences the average atomic mass. Therefore, the average atomic mass is closest to 31, reflecting its higher percent abundance.

Use the table to answer the following question. Based on the percent abundance, what is the identity of the unknown substance?

• Technetium because the average atomic mass is close to 99 amu.

• Vanadium because 16, 17, and 18 add together for a total mass of 51 amu.

• Chlorine because the average of 16, 17, and 18 is 17 which is the atomic number of Chlorine.

• Oxygen because the isotope with the greatest percent abundance is close to its average atomic mass.

Answer explanation

Oxygen is the correct choice because its most abundant isotope closely matches its average atomic mass, indicating a strong correlation between abundance and atomic mass.

Tags

NGSS.HS-PS1-1

Use the table to answer the following question. Which atoms in the table are the same element and with what reasoning?

• Atoms 1 and 2, because they have the same number of protons.

• Atoms 2 and 3, because they have the same number of electrons.

• Atoms 1 and 3, because the sum of all subatomic particles are equal.

• All atoms are the same because they have the same number of neutrons.

Answer explanation

Atoms 1 and 2 are the same element because they have the same number of protons, which defines the element. The number of electrons and neutrons can vary, but the proton count is what determines the element's identity.

Tags

NGSS.MS-PS1-1

Use the models to answer the following question. Which model recognizes the merit of an atom having a dense, positive nucleus that is surrounded by mostly empty space?

• J.J Thomson

• Rutherford

• Bohr

• Current Model

Answer explanation

The Rutherford model describes the atom as having a dense, positively charged nucleus surrounded by mostly empty space, which was a significant advancement over Thomson's plum pudding model.

Tags

NGSS.HS-PS1-8

Use the models to answer the following question. How does the current model show improvement over the previous models of the atom?

• The current model shows protons inside the nucleus.

• The current model shows electrons outside the nucleus.

• The current model shows protons have a positive charge.

• The current model shows electrons in s,p,d,f energy levels.

Answer explanation

The current model improves upon previous models by accurately depicting electrons in s, p, d, f energy levels, which reflects their distribution and energy states, enhancing our understanding of atomic structure.

Tags

NGSS.HS-PS1-8